Projection lens system

ABSTRACT

This invention relates to a projection lens system used for transferring circuit or other patterns from masks, etc. on which the circuit patterns are drawn onto semiconductor wafers by projection photolithography, and provides a projection lens system which makes high resolving power of the order of a few micrometers and wide exposure coverages compatible with each other. 
     This projection lens system includes at least two sets of lens groups, each built up of lenses having concave surfaces located opposite to each other, and includes at least one lens surface of positive refractive power between said two sets of lens groups, said two sets of lens groups all satisfying the following conditions: 
     
         1/L&lt;|φ.sub.1 &lt;20/L                            (1) 
    
     
         1/L&lt;|φ.sub.2 &lt;20/L                            (2) 
    
     wherein φ 1  and φ 2  stand for the respective negative refractive powers of said oppositely located concave surfaces, and L is the distance between object and image.

This is a division of application Ser. No. 07/780,339, filed Oct. 22, 1991, U.S. Pat. No. 5,260,832.

BACKGROUND OF THE INVENTION

The present invention relates to a projection lens system used for transferring circuit or other patterns onto semiconductor wafers through masks, etc.--on which the circuit patterns are drawn--by projection photolithography.

So far, transfer of desired patterns onto integrated circuits such as ICs and LSIs or flat displays built up of liquid crystals has been achieved by non-contact photolithography called the proximity technique or reflecting photolithography called the aligner technique.

Of these, the proximity technique is designed to locate a mask in close proximity to a semiconductor wafer and transfer a circuit pattern drawn on the mask onto the wafer, as set forth in Japanese Provisional Patent Publication No. 50(1975)-115774. In this technique, it is a slight space between the mask and the substrate onto which the pattern is to be transferred that determines transfer resolving power; this space must be very narrow when transfer is to be carried out with high resolving power. However, when the mask is located in too close proximity to or in contact with the substrate, the circuit pattern transferred onto the substrate would be impaired.

In the aligner technique, on the other hand, pattern resolving powers are determined by imagewise numerical aperture, because masks are adapted to be projected onto wafers through a reflecting optical system, as disclosed in Japanese Provisional Patent Publication No. 63(1988)-184328. However, this technique again offers a problem in that no high resolving power can be obtained, because it is impossible to increase the imagewise numerical aperture for the reason that the reflecting optical system is usually an equimultiple one. As the region to be exposed to light, i.e., the image surface increases in area, there is an increase in the expansion of a semiconductor substrate due to the heat of projected light; transfer must be carried out after the alignment of the circuit pattern size by fine adjustment of projecting magnification. However, a major problem with the aligner technique is that a pattern of large size cannot be projected at one time, because it is in principle difficult to vary the projecting magnification in alignment with the expansion of the substrate. In order to solve these problems, the step-and-repeat photolithographic technique with demagnification has been mainly used in recent years. As set forth in Japanese Provisional Patent Publication No. 60( 1985)-195509 and other literature, this technique is designed to project masks onto wafers with suitable demagnification (on the scale of ca. 1 to 2, 3, . . . ) for pattern transfer. This technique enables projecting magnifications to be arbitrarily varied by fine adjustment of a distance between the mask on which a circuit pattern is drawn and the projected image (substrate) and makes it easy to enhance resolving powers by affording a large value for the imagewise numerical aperture of a projection lens, and so will be increasingly used from now on.

However, conventional projection lens systems available with this technique have been found to fall to satisfy both high resolving power (i.e., large numerical aperture) and wide exposure coverages (image heights).

SUMMARY OF THE INVENTION

A principal object of this invention is to provide a projection lens system which makes high resolving power on the order of a few micrometers and wide exposure coverages compatible with each other.

The projection lens system according to this invention is characterized by including at least two sets of lens groups, each built up of lenses whose concave surfaces are opposite to each other, and including at least one lens surface having positive refractive power between the two sets of lens groups.

Referring more specifically to this invention, the curvature of field need be almost completely corrected so as to achieve high resolving power and wide exposure coverages concurrently. As well known in the art, the curvature of field has close relations to the Petzval's sum; the smaller the Petzval's sum the smaller the curvature of field, thus achieving wide exposure coverages. Although it is known that lens arrays having concave surfaces located in opposition to each other may be used as means for correcting the Petzval's sum, difficulty would be encountered in correcting the Petzval's sum with one such array of lenses. The reason is that it may be possible to decrease the Petzval's sum by increasing the negative refractive powers of the oppositely located concave surfaces; however, when the concave surfaces have too high powers, comae occurring thereon are too large to make corrections by other surfaces.

Now, the use of two sets of lens groups, each having concave surfaces located opposite to each other, is envisaged. A problem with such an arrangement, however, is that only the lens group having its concave surfaces giving out divergent bundles of rays are so locally positioned on part of the lens system that there can be no choice but to diminish the negative refractive powers of such concave surfaces so as to allow the refractive power of the overall lens system to get a given value. More exactly, the oppositely located concave surfaces act to decrease the Petzval's sum increase in number, but it is nonetheless impossible to decrease the Petzval's sum because the respective concave surfaces are less capable of making corrections.

According to this invention accomplished with the foregoing in mind, at least one lens surface having positive refractive power is positioned between two sets of lens groups, each having concave surfaces located opposite to each other, thereby making an effective contribution to correcting the Petzval's sum. With this arrangement wherein the two sets of lens groups, each having concave surfaces located opposite to each other, are coaxially positioned with the lens surface having positive refractive power disposed therebetween, the respective concave surfaces of each lens group are allowed to have suitable refractive powers with respect to the Petzval's sum and comae. The "suitable refractive powers" referred to in this disclosure satisfy the following conditions:

    1/L<|φ.sub.1 |<20/L                  (1)

    1/L<|φ.sub.2 |<20/L                  (2)

wherein φ₁ and φ₂ stand for the respective negative refractive powers of the concave surfaces located opposite to each other, and L is the distance between object and image.

At above the upper limits of these conditions, the negative refractive powers of the concave surfaces are too low to make sufficient corrections on the Petzval's sum, leaving behind some curvature of field and so rendering it possible to obtain wide exposure coverages. At below the lower limits, the negative refractive powers are so increased that the Petzval's sum can be corrected, but difficulty is involved in making corrections by other surfaces due to the occurrence of excessive comas.

In order to prevent partial image distortions which may otherwise occur depending upon the flatness of the substrate, it is desired to set up a so-called telecentric system wherein the imagewise exit pupil is designed to lie in the vicinity of the infinite point. According to this invention, a positive lens group is disposed on the image surface of the two sets of lens groups, each built up of concave surfaces located opposite to each other, so as to allow the imagewise exit pupil to lie in the vicinity of the infinite point. This is to focus the exit pupil in the lens system on the infinite point.

Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.

The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 9 are sectional views showing lens arrangements of the first to ninth embodiments of this invention, and

FIGS. 10A to 10F through 18A to 18F are aberration curve diagrams of the 1st to 9th embodiments.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Some embodiments of the projection lens system according to this Invention will now be explained at great length with reference to the drawings.

FIG. 1 is a sectional view showing the lens arrangement of the 1st embodiment, wherein the second and fifth surfaces R2 and R5 and the 16th and 17th surfaces R16 and R17 define oppositely located concave surfaces (shown by φ₁ and φ₂ in the drawing). The 2nd and 5th surfaces R2 and R5 are shown to include a lens of moderate power therebetween, but according to this invention there may be included a lens component of simple structure between the "lens groups, each having concave surfaces located opposite to each other". This lens system is a projection lens with demagnification on a one-to-two scale.

FIG. 2 is a sectional view showing a lens arrangement of the 2nd embodiment, wherein the 5th and 8th surfaces R5 and R8 and the 17th and 18th surfaces R17 and R18 define oppositely disposed concave surfaces. This lens system is again a projection lens with demagnification on a one-to-two scale.

FIG. 3 is a sectional view showing a lens arrangement of the 3rd embodiment, wherein the 5th and 8th surfaces R5 and R8 and the 17th and 20th surfaces R17 and R20 define oppositely disposed concave surfaces. This lens system is an equimultiple projection lens.

All these embodiments are characterized by including a lens group of positive refractive power, built up of at least two lens of positive refract ire powers, between two sets of lens groups, each built up of oppositely disposed concave surfaces, and by meeting the following condition:

    f<L/4                                                      (3)

wherein f is the composite focal length and L is the distance between object and image. This condition implies that unless the lens group of positive refractive power has a certain or higher refractive power, some difficulty is encountered in making satisfactory aberration corrections. Since the respective lens groups, each built up of oppositely disposed concave surfaces, have increased negative refractive powers, the lens group of positive refractive power sandwiched therebetween are located at a position at which marginal rays stand high. The higher the position of a lens where marginal rays stand high, the more it is likely to have an influence on the focal length of the overall lens system, thus allowing the refractive power of the overall system to be born by this lens group of positive refractive power. For that reason, when the positive refractive power of the lens group having positive refractive power diminishes out of condition, it is impossible to increase the refractive powers of the oppositely disposed concave surfaces of the two sets of lens groups; it is impossible to decrease the Petzval's sum.

In each of these embodiments, the imagewise lens group of the lens groups, each built up of oppositely disposed concave surfaces, includes at least three lenses of positive refractive powers and at least one lens of negative refractive power so as to achieve a telecentric system on the image side. Such positive and negative lenses are needed to make satisfactory corrections on spherical aberrations when the pupil in the lens system is focused on the infinite point. For instance, when this group comprises one single lens, the angle of inclination of exit rays is made large by image heights because the spherical aberration of the pupil cannot be well corrected. Thus, when image surfaces are moving to-and-fro in the focal depth, image distortions vary seriously.

FIG. 4 is a sectional view showing a lens arrangement of the 4th embodiment, wherein the 7th and 8th surfaces R7 and R8 and the 13th and 14th surfaces R13 and 14 define oppositely disposed concave surfaces.

FIG. 5 is a sectional view showing a lens arrangement of the 5th embodiment, wherein the 10th and 11th surfaces R10 and R11 and the 16th and 17th surfaces R16 and 17 define oppositely disposed concave surfaces.

FIG. 6 is a sectional view showing a lens arrangement of the 6th embodiment, wherein the 13th and 16th surfaces R13 and R16 and the 19th and 20th surfaces R19 and R20 define oppositely disposed concave surfaces.

FIG. 7 is a sectional view showing a lens arrangement of the 7th embodiment, wherein the 14th and 15th surfaces R14 and R15 and the 24th and 25th surfaces R24 and R25 define oppositely disposed concave surfaces.

FIG. 8 is a sectional view showing a lens arrangement of the 8th embodiment, wherein the 14th and 15th surfaces R14 and R15 and the 24th and 25th surfaces R24 and R25 define oppositely disposed concave surfaces.

FIG. 9 is a sectional view showing a lens arrangement of the 9th embodiment, wherein the 10th and 11th surfaces R10 and R11, the 16th and 17th surfaces R16 and R17 and the 26th and 27th surfaces R26 and 27 define oppositely disposed concave surfaces.

The 4th-9th embodiments are all directed to projection lenses with demagnification on a one-to-five scale. In the lens systems with demagnification on a one-to-five scale, the imagewise principal points of the lenses are closer to images than those in the 1st to 3rd embodiments. In other words, when a positive lens group of positive refractive power that constitutes a major power is located between two sets of lens groups, each comprising oppositely disposed concave surfaces, there is no space for providing a positive lens group to achieve a telecentric construction on the image side. This is because, in each of these embodiments, the two sets of lens groups, each built up of oppositely disposed concave surfaces, are located on the object side of the above-mentioned positive lens group that constitutes a major power of the lens system.

In order to obtain an imagewise numerical aperture (NA) of 0.4 or more, the above-mentioned positive lens group that constitutes a major power is built up of at least four lenses having positive refractive powers, whereby the amount of spherical aberrations caused by the positive lens group that constitutes a major power can be corrected by other lenses.

In order to correct the Petzval's sum more satisfactorily, a lens which has negative refractive power and the concave surface of which faces the image side is provided on the image side of the two sets of lens groups, each built up of oppositely disposed concave surfaces. Making the Petzval's sum good enough and obtaining wide exposure coverages are then achieved by satisfying the following condition:

    1/L<|φ.sub.3 |<20/L                  (4)

wherein φ₃ is the negative refractive power of the additional lens and L is the distance between object and image. The same as referred to in connection with Condition (1) again holds for the upper and lower limits of Condition (4). In order to afford pertinent values for the refractive powers of the two sets of lens groups, each built up of oppositely disposed concave surfaces, and make the amount of comae correctable by other lenses, a lens group built up of at least two lenses of positive refractive powers is disposed on the object side of the above-mentioned sets of lens groups. This lens group having positive refractive power makes it possible to lower the height of off-axial rays when they are incident on the oppositely disposed concave surfaces on the object side. When the incident rays are at a low height, comae are less likely to occur, because even though the oppositely disposed concave surfaces are increased in refractive power by decreasing their radii of curvature, there is a little, if any, difference in the angle of incidence upon the concave surfaces between the upper and lower components of off-axial dependent rays.

Referring to the 10th embodiment, the Petzval's sum is further decreased by using three sets of lens groups, each having concave surfaces disposed opposite to each other.

It is noted that the 7th to 9th embodiments are designed to be used with monochromatic light sources having a very close range of wavelengths, like laser, and are formed of a single glass material.

In each of these embodiments, an imagewise numerical aperture (NA) of 0.45 or more is obtained by disposing an additional lens group comprising at least one lens of negative refractive power on the object side of the lens group comprising at least two lenses of positive refractive powers, which has been disposed on the object side of the two sets of lens groups, each built up of oppositely disposed concave surfaces. This is to correct coma flares occurring on the lens group comprising at least two lenses of positive refractive powers, located on the above-mentioned object side. In addition, the positive refractive power of the lens group located between the two sets of lens groups, each built up of oppositely disposed concave surfaces, is increased to impart proper refractive powers to the oppositely disposed concave surfaces.

The 9th embodiment is constructed as a projection lens system made telecentric on both its sides, wherein the entrance pupil is set at the infinite point.

In the following examples, detailed data will be given.

    ______________________________________                                         Example 1                                                                      f = 211.48  NA = 0.2  IH = 37.5  L = 1000                                      OB = 363.015  SK = 18.185  λ = 436 nm                                   ______________________________________                                         R1 = 290.079   D1 = 17.500  N1 = 1.69299                                       R2 = 138.498   D2 = 8.846                                                      R3 = 507.317   D3 = 17.500  N2 = 1.71756                                       R4 = ∞   D4 = 21.215                                                     R5 = -129.056  D5 = 41.301  N3 = 1.59953                                       R6 = 239.801   D6 = 39.464  N4 = 1.52613                                       R7 = -201.485  D7 = 12.896                                                     R8 = ∞   D8 = 22.500  N5 = 1.52613                                       R9 = -394.840  D9 = 1.250                                                      R10 = 292.481  D10 = 25.000 N6 = 1.52613                                       R11 = -610.192 D11 = 1.250                                                     R12 = 250.061  D12 = 27.500 N7 = 1.52613                                       R13 = -746.631 D13 =  35.913                                                   R14 = 165.337  D14 = 39.178 N8 = 1.52613                                       R15 = -178.430 D15 = 13.750 N9 = 1.59953                                       R16 = 103.371  D16 = 99.911                                                    R17 = -97.752  D17 = 10.000 N10 = 1.54529                                      R18 = 343.137  D18 = 13.691                                                    R19 = -341.327 D19 = 18.750 N11 = 1.71221                                      R20 = -155.958 D20 = 35.863                                                    R21 = 132.625  D21 = 27.500 N12 = 1.52613                                      R22 = ∞  D22 = 1.250                                                     R23 = 239. 402 D23 = 20.000 N13 = 1.61529                                      R24 = ∞  D24 = 1.250                                                     R25 = 219.047  D25 = 48.519 N14 = 1.61529                                      R26 = ∞  D26 = 7.014                                                     R27 = -234.923 D27 = 10.000 N15 = 1.71756                                      R28 = 259.518                                                                  ______________________________________                                         φ.sub.1 (R2) = -0.005, φ.sub.2 (R5) = -0.0046                          φ.sub.1 (R16) = -0.0058, φ.sub.2 (R17) = -0.0056                       ______________________________________                                         Example 2                                                                      f = 215.03  NA = 0.18  IH = 50  L = 1000                                       OB = 336.094  SK = 15.000  λ = 436 nm                                   ______________________________________                                         R1 = 427.197   D1 = 15.000  N1 = 1.57082                                       R2 = 147.578   D2 = 19.888  N2 = 1.62364                                       R3 = ∞   D3 = 3.750                                                      R4 = 156.400   D4 = 15.000  N3 = 1.62364                                       R5 = 95.679    D5 = 23.118                                                     R6 = -103.846  D6 = 15.000  N4 = 1.61529                                       R7 = -90.413   D7 = 9.643                                                      R8 = -83.274   D8 = 27.219  N5 = 1.59953                                       R9 = 426.489   D9 = 43.157  N6 = 1.52613                                       R10 = -159.199 D10 = 44.347                                                    R11 = 825. 646 D11 = 22.442 N7 = 1.63619                                       R12 = -282.360 D12 = 1.250                                                     R13 = 227.045  D13 = 31.218 N8 = 1.61529                                       R14 = -749.008 D14 = 43.166                                                    R15 = 184.718  D15 = 30.140 N9 = 1.52613                                       R16 = -227.718 D16 = 15.000 N10 = 1.66362                                      R17 = 133.563  D17 = 121.146                                                   R18 = -101.157 D18 = 15.000 N11 = 1.58406                                      R19 = 875.000  D19 = 8.592                                                     R20 = -475.291 D20 = 20.000 N12 = 1.71221                                      R21 = -214.958 D21 = 1.250                                                     R22 = 167.754  D22 = 33.383 N13 = 1.54529                                      R23 = -449.144 D23 = 1.250                                                     R24 = 490.443  D24 = 21.250 N14 = 1.71221                                      R25 = -847.568 D25 = 1.250                                                     R26 = 269.443  D26 = 20.000 N15 = 1.71221                                      R27 = ∞  D27 = 7.338                                                     R28 = -386.590 D28 = 15.000 N16 = 1.52613                                      R29 = 875.000  D29 =  11.610                                                   R30 = -208.684 D30 = 12.500 N17 = 1.52613                                      R31 = ∞                                                                  ______________________________________                                         φ.sub.1 (R5) = -0.0065, φ.sub.2 (R8) = -0.0072,                        φ.sub.1 (R17) = -0.005, φ.sub.2 (R18) = -0.0058                        ______________________________________                                         Example 3                                                                      f = 310. 93  NA = 0.1  IH = 88  L = 1000                                       OB = 280.813  SK = 15.00  A = 436 nm                                           ______________________________________                                         R1 = 292.620   D1 = 18.811  N1 = 1.57082                                       R2 = -159.166  D2 = 15.000  N2 = 1.62364                                       R3 = -1869.713 D3 = 1.250                                                      R4 = 114.734   D4 = 15.000  N3 = 1.62364                                       R5 = 81.531    D5 = 19.319                                                     R6 = -89.379   D6 = 28.913  N4 = 1.61529                                       R7 = -87.779   D7 = 14.214                                                     R8 = -79.176   D8 = 15.006  N5 = 1.59953                                       R9 = -87.304   D9 = 21.379  N6 = 1.52613                                       R10 = -150.014 D10 = 33.438                                                    R11 = 712.082  D11 = 24.950 N7 = 1.63619                                       R12 = -289.529 D12 = 1.946                                                     R13 = 321.409  D13 = 31.266 N8 = 1.61529                                       R14 = -318.064 D14 = 26.097                                                    R15 = 194.500  D15 = 39.408 N9 = 1.52613                                       R16 = -161.670 D16 = 15.251 N10 = 1.66362                                      R17 = 133.903  D17 = 131.310                                                   R18 = -113.561 D18 = 15.000 N11 = 1.58406                                      R19 = -175.912 D19 = 35.716                                                    R20 = -122.171 D20 = 15.000 N12 = 1.71221                                      R21 = -232.823 D21 = 42.036                                                    R22 = 778.470  D22 = 31.449 N13 = 1.54529                                      R23 = -356.749 D23 = 1.250                                                     R24 = 1086.864 D24 = 27.302 N14 = 1.71221                                      R25 =  -450.133                                                                               D25 = 1.250                                                     R26 = 489.065  D26 = 30.751 N15 = 1.71221                                      R27 = -488.224 D27 = 4.415                                                     R28 = -402.456 D28 = 15.000 N16 = 1.52613                                      R29 = 486.544  D29 = 19.965                                                    R30 = -461.652 D30 = 12.500 N17 = 1.52613                                      R31 = ∞                                                                  ______________________________________                                         φ.sub.1 (R5) = -0.0076, φ.sub.2 (R8) = -0.0076,                        φ.sub.1 (R17) = -0.00495, φ.sub.2 (R20) = -0.0058                      ______________________________________                                         Example 4                                                                      f = 131.35  NA = 0.42  IH = 17.6  L = 1000                                     OB = 233.494  SK = 19.762  A = 365 nm                                          ______________________________________                                         R1 = ∞   D1 = 25.014  N1 = 1.66650                                       R2 = -540.172  D2 = 0.502                                                      R3 = 314.013   D3 = 23.561  N2 = 1.53607                                       R4 =  -1052.536                                                                               D4 = 0.500                                                      R5 = 141.696   D5 = 28.894  N3 = 1.66650                                       R6 = 250.725   D6 = 16.200  N4 = 1.62747                                       R7 = 82.055    D7 = 23.237                                                     R8 = -248.492  D8 = 9.743   N5 = 1.53607                                       R9 = 155.078   D9 = 42.165                                                     R10 = 1411.311 D10 = 43.265 N6 = 1.53607                                       R11 = -197.016 D11 = 0.720                                                     R12 = 1887.223 D12 = 9.992  N7 = 1.53607                                       R13 = 128.923  D13 = 26.295                                                    R14 = -83.854  D14 = 29.985 N8 = 1.63595                                       R15 = 179.127  D15 = 52.329 N9 = 1.53607                                       R16 = -153.936 D16 = 12.067                                                    R17 = -405.392 D17 = 21.223 N10 = 1.53607                                      R18 = -236.191 D18 = 0.166                                                     R19 = 487.323  D19 = 26.099 N11 = 1.53607                                      R20 = -468.313 D20 = 39.652                                                    R21 = 304.311  D21 = 33.362 N12 = 1.53607                                      R22 = -716.692 D22 = 0.627                                                     R23 = 230.393  D23 = 30.350 N13 = 1.53607                                      R24 = -1013.566                                                                               D24 = 2.491                                                     R25 = 129.171  D25 = 45.421 N14 = 1.53607                                      R26 = -265.302 D26 = 10.087 N15 = 1.61936                                      R27 = 80.350   D27 = 46.038                                                    R28 = -127.941 D28 = 9.788  N16 = 1.62757                                      R29 = 151.523  D29 = 5.853                                                     R30 = 409.679  D30 = 32.322 N17 = 1.53607                                      R31 = -196.968 D31 = 3.703                                                     R32 = 87.936   D32 = 49.116 N18 = 1.53607                                      R33 = -552.433 D33 = 0.642                                                     R34 = 88.909   D34 = 31.195 N19 = 1.53607                                      R35 = ∞  D35 = 3.982                                                     R36 = -171.383 D36 = 10.117 N20 = 1.66651                                      R37 = ∞                                                                  ______________________________________                                         φ.sub.1 (R7) = -0.0077, φ.sub.2 (R8) = -0.0022,                        φ.sub.1 (R13) = -0.0042, φ.sub.2 (R14) = -0.0080,                      φ.sub.1 '(R27) = -0.0077                                                   ______________________________________                                         Example 5                                                                      f = 125.51  NA = 0.55  IH = 17.8  L = 1000                                     OB = 209.791  SK = 15.000  λ = 365 nm                                   ______________________________________                                         R1 = -160.871  D1 = 12.500  N1 = 1.53577                                       R2 = -3042.237 D2 = 37.543  N2 = 1.68816                                       R3 = -276.972  D3 = 1.250                                                      R4 = 924.249   D4 = 26.108  N3 = 1.70826                                       R5 = -517.336  D5 = 1.250                                                      R6 = 360.906   D6 = 27.247  N4 = 1.70826                                       R7 = -1284.981 D7 = 1.250                                                      R8 = 291.736   D8 = 51.175  N5 = 1.64177                                       R9 = -123.660  D9 = 22.935  N6 = 1.64035                                       R10 =  75. 015 D10 = 31.102                                                    R11 = -136.141 D11 = 12.500 N7 = 1.53577                                       R12 = 198.932  D12 = 1.250                                                     R13 = 156.713  D13 = 75.896 N8 = 1.69377                                       R14 = -135.199 D14 = 4.396                                                     R15 = -108.356 D15 = 12.500 N9 = 1.55881                                       R16 = 174.685  D16 = 33.885                                                    R17 = -80.542  D17 = 12.500 N10 = 1.66640                                      R18 = 1057.599 D18 = 43.876 N11 = 1.53577                                      R19 = -136.636 D19 = 1.250                                                     R20 = -350.875 D20 = 26.069 N12 = 1.65599                                      R21 = -195.286 D21 = 1.250                                                     R22 = 1984.422 D22 = 38.999 N13 = 1.60189                                      R23 = -258.154 D23 = 1.250                                                     R24 = 361.244  D24 = 34.469 N14 = 1.67717                                      R25 = -1057.393                                                                               D25 = 1.250                                                     R26 = 196.491  D26 = 35.213 N15 = 1.60763                                      R27 =  1206.640                                                                               D27 = 1.250                                                     R28 = 137.471  D28 = 54.194 N16 = 1.53577                                      R29 = -609.635 D29 = 12.500 N17 = 1.67508                                      R30 = 90.424   D30 = 18.571                                                    R31 = 11044.575                                                                               D31 = 12.500 N18 = 1.66640                                      R32 = 98.328   D32 = 12.241                                                    R33 = 592.755  D33 = 17.335 N19 = 1.70826                                      R34 = -435.824 D34 = 1.250                                                     R35 = 95.932   D35 = 73.213 N20 = 1.62930                                      R36 = 124.190  D36 = 1.250                                                     R37 = 58.297   D37 = 21.991 N21 = 1.57066                                      R38 = ∞                                                                  ______________________________________                                         φ.sub.1 (R10) = -0.0085, φ.sub.2 (R11) = -0.0039,                      φ.sub.1 (R16) = -0.0032, φ.sub.2 (R17) = -0.0081,                      φ.sub.3 (R30) = -0.0075                                                    ______________________________________                                         Example 6                                                                      f = 125.49  NA = 0.45  IH = 20.8   L = 1000                                    OB = 49.834  SK = 6.644  λ= 365 nm                                      ______________________________________                                         R1 = 168.112   D1 = 65.605  N1 = 1.62743                                       R2 = 887.936   D2 = 3.384                                                      R3 = 1461.620  D3 = 13.289  N2 = 1.64868                                       R4 = 137.202   D4 = 32.228                                                     R5 = -467.702  D5 = 13.289  N3 = 1.58675                                       R6 = 314.339   D6 = 38.655                                                     R7 = 564.420   D7 = 29.068  N4 = 1.66640                                       R8 = -333.913  D8 = 0.166                                                      R9 = 290.824   D9 = 25.751  N5 = 1.66640                                       R10 = -1710.394                                                                               D10 = 0.166                                                     R11 = 144.337  D11 = 26.999 N6 = 1.66640                                       R12 = 424.669  D12 = 13.289 N7 = 1.62743                                       R13 = 80.696   D13 = 25.985                                                    R14 = -1722.441                                                                               D14 = 13.289 N8 = 1.53577                                       R15 = 278.635  D15 = 27.968                                                    R16 = - 202.476                                                                               D16 = 30.050 N9 = 1.53577                                       R17 = -140.629 D17 = 0.532                                                     R18 = -363.277 D18 = 13.289 N10 = 1.62743                                      R19 = 218.903  D19 = 29.504                                                    R20 = -83.243  D20 = 13.289 N11 = 1.66640                                      R21 = 283.775  D21 = 54.746 N12 = 1.53577                                      R22 = -148.014 D22 = 0.238                                                     R23 = -1124.876                                                                               D23 = 22.658 N13 = 1.53577                                      R24 = -318.918 D24 = 0.166                                                     R25 = -1458.495                                                                               D25 = 24.222 N14 = 1.53577                                      R26 = -330.471 D26 = 0.166                                                     R27 = 755.829  D27 = 36.611 N15 = 1.62743                                      R28 = -278.914 D28 = 0.166                                                     R29 = 255.070  D29 = 29.666 N16 = 1.62743                                      R30 = 5559.544 D30 = 0.252                                                     R31 = 142.643  D31 = 73.127 N17 = 1.53577                                      R32 = -338.766 D32 = 13.289 N18 = 1.63609                                      R33 = 83.174   D33 = 19.323                                                    R34 = -230.675 D34 = 13.289 N19 = 1.63609                                      R35 = 165.095  D35 = 6.212                                                     R36 = 966.343  D36 = 46.467 N20 = 1.66645                                      R37 = -306.352 D37 = 0.166                                                     R38 = 153.907  D38 = 90.916 N21 = 1.62743                                      R39 = 384.718  D39 = 0.166                                                     R40 = 95.792   D40 = 26.859 N22 = 1.53577                                      R41 = ∞  D41 = 0.166                                                     R42 = 98.954   D42 = 51.658 N23 = 1.61935                                      R43 = 926.333  D43 = 3.877                                                     R44 = -272.350 D44 = 13.289 N24 = 1.66640                                      R45 = ∞                                                                  ______________________________________                                         φ.sub.1 (R13) = -0.0078, φ.sub.2 (R16) = -0.0027,                      φ.sub.1 (R19) = -0.0029, φ.sub.2 (R20) = -0.0080,                      φ.sub.3 (R33) = -0.0077                                                    ______________________________________                                         Example 7                                                                      f = 92.56  NA = 0.48  IH = 18.1  L = 1000                                      OB = 150.000  SK = 15.046  λ = 248 nm                                   ______________________________________                                         R1 = 1439.092  D1 = 13.876  N1 = 1.50838                                       R2 = -960.360  D2 = 0.125                                                      R3 = 666.083   D3 = 12.500  N2 = 1.50838                                       R4 = 182.084   D4 = 14.112                                                     R5 = 1896.200  D5 = 12.500  N3 = 1.50838                                       R6 = 212.178   D6 = 66.696                                                     R7 = 383.213   D7 = 26.225  N4 = 1.50838                                       R8 = -405.603  D8 = 0.125                                                      R9 = 278.896   D9 = 25.759  N5 = 1.50838                                       R10 = -671.954 D10 = 0.125                                                     R11 = 212.136  D11 = 33.976 N6 = 1.50838                                       R12 = -543.385 D12 = 0.125                                                     R13 = 2010.730 D13 = 12.500 N7 = 1.50838                                       R14 = 84.549   D14 = 33.039                                                    R15 =  -124.255                                                                               D15 = 12.500 N8 = 1.50838                                       R16 = 152.113  D16 = 19.745                                                    R17 = 1275.450 D17 = 13.050 N9 = 1.50838                                       R18 = -627.003 D18 = 15.823                                                    R19 = 732.677  D19 = 17.262 N10 = 1.50838                                      R20 = -393.765 D20 = 0.125                                                     R21 = 449.220  D21 = 26.819 N11 = 1.50838                                      R22 = -178.779 D22 = 53.499                                                    R23 = 365.033  D23 = 12.500 N12 = 1.50838                                      R24 = 118.635  D24 = 25.300                                                    R25 = -99.983  D25 = 38.782 N13 = 1.50838                                      R26 = 1359.503 D26 = 37.528                                                    R27 = -922.878 D27 = 40.110 N14 = 1.50838                                      R28 = -201.836 D28 = 0.125                                                     R29 = 1275.499 D29 = 29.638 N15 = 1.50838                                      R30 = -257.024 D30 = 0.125                                                     R31 = 326.989  D31 = 30.482 N16 = 1.50838                                      R32 = -661.938 D32 = 0.125                                                     R33 = 177.265  D33 = 26.480 N17 = 1.50838                                      R34 = 500.907  D34 = 0.125                                                     R35 = 121.991  D35 = 61.152 N18 = 1.50838                                      R36 = 70.628   D36 = 26.894                                                    R37 = -1299.508                                                                               D37 = 12.500 N19 = 1.50838                                      R38 = 2084.322 D38 = 0.125                                                     R39 = 60.854   D39 = 14.152 N20 = 1.50838                                      R40 = 62.437   D40 = 11.022                                                    R41 = 134.373  D41 = 27.397 N21 = 1.50838                                      R42 = 133.048  D42 = 0.125                                                     R43 = 68.073   D43 = 16.337 N22 = 1.50838                                      R44 = 356.069  D44 = 3.427                                                     R45 = -286.670 D45 = 10.000 N23 = 1.50838                                      R46 = 7501.444                                                                 ______________________________________                                         φ.sub.1 (R14) = -0.0060, φ.sub.2 (R15) = -0.0041,                      φ.sub.1 (R24) = -0.0043, φ.sub.2 (R25) = -0.0051,                      φ.sub.3 (R36) = -0.0072                                                    ______________________________________                                         Example 8                                                                      f = 91.09  NA = 0.48  IH = 18.1  L = 1000                                      OB = 136.341  SK = 14.812  λ = 248 nm                                   ______________________________________                                         R1 = 1332.715  D1 = 19.816  N1 = 1.50838                                       R2 = -565.036  D2 = 0.125                                                      R3 = 1213.556  D3 = 12.500  N2 = 1.50838                                       R4 = 178.094   D4 = 17.614                                                     R5 = 1737.407  D5 = 12.500  N3 = 1.50838                                       R6 = 217.577   D6 = 68.375                                                     R7 = 398.868   D7 = 27.700  N4 = 1.50838                                       R8 = -414.411  D8 = 0.125                                                      R9 = 273.365   D9 = 24.060  N5 = 1.50838                                       R10 = -694.657 D10 = 0.125                                                     R11 = 214.700  D11 = 32.882 N6 = 1.50838                                       R12 = -521.898 D12 = 1.060                                                     R13 = 3636.652 D13 = 12.500 N7 =  1.50838                                      R14 = 85.823   D14 = 31.825                                                    R15 = -124.767 D15 = 12.500 N8 = 1.50838                                       R16 = 151.401  D16 = 19.805                                                    R17 = 1233.963 D17 = 13.092 N9 = 1.50838                                       R18 = -631.567 D18 = 15.843                                                    R19 = 703.428  D19 = 17.030 N10 = 1.50838                                      R20 = -402.530 D20 = 0.125                                                     R21 = 442.276  D21 = 29.028 N11 = 1.50838                                      R22 = -180.319 D22 = 52.693                                                    R23 = 362.711  D23 = 12.500 N12 = 1.50838                                      R24 = 118.168  D24 = 25.749                                                    R25 = -100.287 D25 = 38.227 N13 = 1.50838                                      R26 = 1003.801 D26 = 37.669                                                    R27 = -1240.566                                                                               D27 = 40.379 N14 = 1.50838                                      R28 = -203.209 D28 = 0.404                                                     R29 = 1276.499 D29 = 30.364 N15 = 1.50838                                      R30 = -257.384 D30 = 0.125                                                     R31 = 321.056  D31 = 29.361 N16 = 1.50838                                      R32 = -691.355 D32 = 0.125                                                     R33 = 172.662  D33 = 30.058 N17 = 1.50838                                      R34 = 466.284  D34 = 0.125                                                     R35 = 119.054  D35 = 55.556 N18 = 1.50838                                      R36 = 70.157   D36 = 26.680                                                    R37 = -1400.393                                                                               D37 = 12.500 N19 = 1.50838                                      R38 = 1663.520 D38 = 0.125                                                     R39 = 60.955   D39 = 14.621 N20 = 1.50838                                      R40 = 62.656   D40 = 11.601                                                    R41 = 137.312  D41 = 28.753 N21 = 1.50838                                      R42 = 131.425  D42 = 0.125                                                     R43 = 68.465   D43 = 18.479 N22 = 1.50838                                      R44 = 434.028  D44 = 2.997                                                     R45 = -244.457 D45 = 10.000 N23 = 1.50838                                      R46 = -4672.849                                                                ______________________________________                                         φ.sub.1 (R14) = -0.0059, φ.sub.2 (R15) = -0.0041,                      φ.sub.1 (R24) =  -0.0043, φ.sub.2 (R25) = -0.0051,                     φ.sub.3 (R36) = -0.0073                                                    ______________________________________                                         Example 9                                                                      f = 1301.98  NA = 0.48  IH = 14.5  L = 1000                                    OB = 163.364  SK = 12.420  λ = 248 nm                                   ______________________________________                                         R1 = 785.237   D1 = 10.000  N1 = 1.50838                                       R2 = 226.496   D2 = 35.207                                                     R3 = 338.103   D3 = 33.119  N2 = 1.50838                                       R4 = -427.697  D4 = 0.100                                                      R5 = 220.682   D5 = 32.878  N3 = 1.50838                                       R6 = -1689.440 D6 = 0.100                                                      R7 = 538.565   D7 = 16.636  N4 = 1.50838                                       R8 = -2998.116 D8 = 42.310                                                     R9 = 1798.948  D9 = 43.869  N5 = 1.50838                                       R10 = 86.594   D10 = 28.437                                                    R11 = -191.459 D11 = 10.000 N6 = 1.50838                                       R12 =  -365.426                                                                               D12 = 6.206                                                     R13 = 205.426  D13 = 21.847 N7 = 1.50838                                       R14 = -235.078 D14 = 0.100                                                     R15 = 140.249  D15 = 29.042 N8 = 1.50838                                       R16 = 71.962   D16 = 23.223                                                    R17 = -103.352 D17 = 10.000 N9 = 1.50838                                       R18 = 291.836  D18 = 21.563                                                    R19 = -169.640 D19 = 13.859 N10 = 1.50838                                      R20 = -146.345 D20 = 1.260                                                     R21 = 548.483  D21 = 14.130 N11 = 1.50838                                      R22 = -286.748 D22 = 0.100                                                     R23 = 370.410  D23 = 17.795 N12 = 1.50838                                      R24 = -192.733 D24 = 0.100                                                     R25 = 289.711  D25 = 46.190 N13 = 1.50838                                      R26 = 98.118   D26 = 23.251                                                    R27 = -93.137  D27 = 27.168 N14 = 1.50838                                      R28 = 696.410  D28 = 35.100                                                    R29 = -2198.585                                                                               D29 = 41.200 N15 = 1.50838                                      R30 = -183.512 D30 = 5.455                                                     R31 = 960.840  D31 = 28.000 N16 = 1.50838                                      R32 = -248.042 D32 = 0.100                                                     R33 = 283.931  D33 = 29.471 N17 = 1.50838                                      R34 = -582.356 D34 = 0.100                                                     R35 = 149.928  D35 = 37.042 N18 = 1.50838                                      R36 = 467.490  D36 = 0.481                                                     R37 = 97.951   D37 = 50.000 N19 = 1.50838                                      R38 = 62.066   D38 = 20.697                                                    R39 = 8857.666 D39 = 10.000 N20 = 1.50838                                      R40 = 239.275  D40 = 0.100                                                     R41 = 86.347   D41 = 11.242 N21 = 1.50838                                      R42 = 117.960  D42 = 0.100                                                     R43 = 96.904   D43 = 19.741 N22 = 1.50838                                      R44 = 79.928   D44 = 1.583                                                     R45 = 61.664   D45 = 14.024 N23 = 1.50838                                      R46 = 2778.127 D46 = 2.290                                                     R47 = -193.684 D47 =  9.000 N24 = 1.50838                                      R48 = 543.831                                                                  ______________________________________                                         φ.sub.1 (R10) = -0.0058, φ.sub.2 (R11) = -0.0027,                      φ.sub.1 (R16) = -0.0036, φ.sub.2 (R17) = -0.0071,                      φ.sub.1 (R26) = -0.0052, φ.sub.2 (R27) = -0.0055,                      φ.sub.3 (R38) = -0.0082                                                    ______________________________________                                    

The abbreviations referred to in the examples stand for: R: curvature of each surface, D: surface separation, N: refractive index, f: focal length of the overall lens system, NA: imagewise numerical aperture, L: distance between object and image, OB: object position, SK: image position, λ: reference wavelength, and φ(R): refractive power of that surface.

How aberrations are corrected in the 1st to 9th embodiments is illustrated in FIGS. 10A to 10F through 18A to 18F.

As explained above, the present invention can successfully provide a projection lens system having wide exposure coverage and resolving power that is high in a sense of being corrected to substantially aplanatic conditions. 

What is claimed is:
 1. A projection lens system comprising:first and second lens groups, each of said first and second lens groups including lens components having concave surfaces located opposite to each other; at least one lens component having a surface with a positive refractive power disposed between said first and second lens groups; and a third lens group disposed on an object side of said first and second lens groups and having at least two lens components each with a positive refractive power.
 2. A projection lens system as claimed in claim 1, wherein a distance between an object and an image has a specific value, and said first and second lens groups satisfy the following conditions (1) and (2)

    1/L<|φ.sub.1 |<20/L                  (1)

    1/L<|φ.sub.2 |<20/L                  (2)

where φ₁ and φ₂ represent respective negative refractive powers of said facing concave surfaces, and L is said distance between said object and said image.
 3. A projection lens system as claimed in claim 2, wherein a lens component having a concave surface on an image side is disposed on said image side of said first and second lens groups, said concave surface satisfying the following condition (5):

    1/L<|φ.sub.3 |<20/L                  (5)

where φ₃ is a refractive power of said concave surface.
 4. A projection lens system as claimed in claim 3, further comprising a sixth lens group including at least one lens component having a negative refractive power disposed on said object side of said first and second lens groups.
 5. A projection lens system as claimed in claim 4, further comprising a seventh lens group, said seventh lens group including lens components having concave surfaces located opposite to each other.
 6. A projection lens system as claimed in claim 5, wherein all lens elements are formed of a same vitreous material.
 7. A projection lens system as claimed in claim 4, wherein all lens elements are formed of a same vitreous material.
 8. A projection lens system as claimed in claim 3, further comprising a seventh lens group, said seventh lens group including lens components having concave surfaces located opposite to each other.
 9. A projection lens system as claimed in claim 8, wherein all lens elements are formed of a same vitreous material.
 10. A projection lens system as claimed in claim 3, wherein all lens elements are formed of a same vitreous material.
 11. A projection lens system as claimed in claim 2, further comprising a sixth lens group including at least one lens component having a negative refractive power disposed on said object side of said first and second lens groups.
 12. A projection lens system as claimed in claim 11, further comprising a seventh lens group, said seventh lens group including lens components having concave surfaces located opposite to each other.
 13. A projection lens system as claimed in claim 12, wherein all lens elements are formed of a same vitreous material.
 14. A projection lens system as claimed in claim 11, wherein all lens elements are formed of a same vitreous material.
 15. A projection lens system as claimed in claim 2, further comprising a seventh lens group, said seventh lens group including lens components having concave surfaces located opposite to each other.
 16. A projection lens system as claimed in claim 15, wherein all lens elements are formed of a same vitreous material.
 17. A projection lens system as claimed in claim 2, wherein all lens elements are formed of a same vitreous material.
 18. A projection lens system as claimed in claim 2, further comprising:a fourth lens group having a positive refractive power and including at least two lens components having a positive refractive power disposed between said first and second lens groups; said fourth lens group satisfying the following condition (3):

    f<L/4                                                      (3)

where f is a composite focal length of said fourth lens group.
 19. A projection lens system as claimed in claim 18, wherein all lens elements are formed of a same vitreous material.
 20. A projection lens system as claimed in claim 18, further comprising a fifth lens group including at least four lens components having a positive refractive power disposed on an image side of said first and second lens units.
 21. A projection lens system as claimed in claim 20, further comprising a sixth lens group including at least one lens component having a negative refractive power disposed on said object side of said first and second lens groups.
 22. A projection lens system as claimed in claim 21, further comprising a seventh lens group, said seventh lens group including lens components having concave surfaces located opposite to each other.
 23. A projection lens system as claimed in claim 22, wherein all lens elements are formed of a same vitreous material.
 24. A projection lens system as claimed in claim 21, wherein all lens elements are formed of a same vitreous material.
 25. A projection lens system as claimed in claim 20, further comprising a seventh lens group, said seventh lens group including lens components having concave surfaces located opposite to each other.
 26. A projection lens system as claimed in claim 25, wherein all lens elements are formed of a same vitreous material.
 27. A projection lens system as claimed in claim 20, wherein all lens elements are formed of a same vitreous material.
 28. A projection lens system as claimed in claim 20, wherein a lens component having a concave surface on an image side is disposed on said image side of said first and second lens groups, and said concave surface satisfies the following condition (4):

    1/L<|φ.sub.3 |<20/L                  (4)

where φ₃ is a refractive power of said concave surface.
 29. A projection lens system as claimed in claim 28, wherein a sixth lens group including at least one lens component having a negative refractive power is disposed on said object side of said first and second lens groups.
 30. A projection lens system as claimed in claim 29, wherein all lens elements are formed of a same vitreous material.
 31. A projection lens system as claimed in claim 29, further comprising a seventh lens group, said seventh lens group including lens components having concave surfaces located opposite to each other.
 32. A projection lens system as claimed in claim 31, wherein all lens elements are formed of a same vitreous material.
 33. A projection lens system as claimed in claim 28, wherein all lens elements are formed of a same vitreous material.
 34. A projection lens system as claimed in claim 28, further comprising a seventh lens group, said seventh lens group including lens components having concave surfaces located opposite to each other.
 35. A projection lens system as claimed in claim 34, wherein all lens elements are formed of a same vitreous material.
 36. A projection lens system comprising:first and second lens groups, each of said first and second lens groups including lens components having concave surfaces located opposite to each other; and a third lens group disposed on an object side of said first and second lens groups and having at least two lens components each with a positive refractive power. 